A number of metals, alloys and intermetallic compounds are known which will store hydrogen in chemical combination and which will release the chemically combined hydrogen under appropriate conditions of temperature and pressure. It is advantageous to be able to store and release hydrogen over a range of moderate temperatures, for example, from 0.degree. C. to not significantly greater than perhaps 95.degree. C. and at pressures ranging from pressures greater than atmospheric (but not enormously greater) down to sub-atmospheric pressures. These conditions are advantageous because the hydrogen can then be recovered using water as a heat exchange medium and at pressures which are commonly employed in industry for various purposes.
It is important to realize, however, that the convenience of low temperature, moderate pressure delivery of hydrogen must be obtainable at a reasonable cost and without the need of critical hydrogen purification steps to avoid poisoning the storage medium. As of the present time, applicant is unaware of any hydride storage system which meets all of the aforestated requirements to the full satisfaction of the workers in the art. In particular, the alloy system apparently closest to the present invention in chemical composition, i.e., La-Ni-Al, is much more expensive and requires much higher temperatures during desorption of hydrogen to provide the advantageous desorption pressure range achieved by the alloys of the present invention. The alloy system apparently closest to the present invention with respect to conditions of absorption and desorption, i.e., LaNi.sub.5 is much more expensive.